People sometimes (in movies, for instance) go away for a time and come back completely changed. I think this is probably the exception rather than the norm. People learn to behave (I am theorising) in a certain way in particular surroundings and these behaviours are sticky – once learnt they are hard to unlearn, even with a long period of time spent elsewhere. You have behaviour-memory as it were.
I recently moved in with my parents after nearly two years abroad. I thought that in that time I had grown up and become more mature. But I soon found that, being in my parents’ house again, I quickly took to doing things the same way I had done them before, as if two years had not even passed. Along with the old rhythm came old habits and old patterns of behaviour. I found myself getting annoyed at the same little things, losing my temper for the same reasons, acting about as maturely as when I had set off. It seems that I will actually have to do the hard work and consciously change my habits.
Perhaps this behaviour-memory is why people report feeling like children again when they go back to their parents. It’s not just that their parents treat them like children. It’s that they also, not fully consciously, act like children, as if they had never really left.
I think the most I gained from my time abroad was the desire to be more mature. Actually being more mature will require breaking my habits.